Trimmer condenser



1937- 1.. c. JOHNSON TRIMMER CONDENSER Filed F eb. 26, 1936 .II' I java/22 0x1- [awrezzde C (770 5d r 777a @Wf Patented Jan. 12, 1937 Lawrence C. Johnson, Chicago, Ill. Application February 26, 1936, Serial No. 65,751

4 c aims. (01. 175-415) The present invention relatesto electrical condensers, and is particularly concerned with the type of condenser which is known as a trimmer condenser and adapted to be used in electrical circuits where a relatively small adjustable condenser is necessary, as, for example, in a radio receiving set.

One of the objects of the invention is the provision of an improved trimmer condenser, all of the parts okwhich are adapted to be made by stamping or punching operations and in which the parts are sosupported that the capacity of the condenser is not affected by the pull exerted upon the electrical connectors of the trimmer condenser by the leads which are attached thereto.

In the devices of the prior art, condensers of integral metal tongues punched out of the body of the uppermost condenser plate and riveted or otherwise secured to an insulating support.

The plate referred to was then supported adjacent the other or lower condenser plate by a pair of resilient arms which are integral extensions from the part of the plate which is used as an electrical connector.

In the devices of the prior art much of the body of the upper plate was removed to form these integral attaching tongues, and the remaining portion of the body of the plate adjacent the point of attachment was such that any pull exerted upon the connector was transmitted up through the spring arms to the upper connector plate, varying the tension of the spring arms which support the connector plate and varying the capacity of the condenser.

The adjustment of suchtrimmer condensers is i so critical that even the pull of attaching leads on the connectors was sufficient to throw the trimmer condenser out of adjustment, due to the construction and arrangement of the supporting parts for the plates in the devices of the prior art.

One of the objects of the invention isthe provision of an improved trimmer condenser in which the removable condenser plate is so supported that its adjustment :cannot be affected by any force which might be applied to the connectors in the normal operation or use of the condenser.

Another object of the invention is the provision of an improved trimmer condenser in which the action of the movable condenser plate is wholly independent of any normal forces applied to the connector members whichiorm an integral part of such condenser plates.

Another object and advantage oi. the invent'on is the provision of an improved trimmer condenser arrangement which may be constructed very economically, due to the fact that all of the parts are made or assembled by punching, stamping or riveting operations.

Other objects and advantages of the invention will be apparent from the accompanying drawing and the following description, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the single sheet of drawings,

Fig. 1 is a top plan view of a bank of trimmer condensers constructed according to the present invention and supported upon a strip of insulating fiber or Bakelite;

Fig. 2 is an enlarged top plan view of a single trimmer condenser embodying the invention and this typehave been provided with one or more having tor its support a porcelain block;

Fig. 3'is a sectional view, taken on the plane of the line 33 of Fig. 2, looking in the direction of the arrows, showing the details of construction of the trimmer condenser of Fig. 2;

Fig. 4 is a rear plan view of a trimmer condenser constructed according to the present invention, taken from the bottom of Fig. 2;

Fig. 5 is a fragmentary sectional view taken on the plane of the line 5-5 of Fig. 4, looking in the direction of the arrows.

Referring to Figs. 1 and 2, it will be observed that the present condensers may be supplied in single units or in banks of condensers. Where banks of condensers are employed, the condenser plates are all supported upon a single strip of insulating material III, each of the respective condenser units being indicated in its entirety by the numeral II. In such case, the additional units are merely duplicates of the single units, and the construction shown in Fig. 1 differs from that of Fig. 2 only in the use of an elongated insulating supporting" strip l0, instead of the, porcelain block I! used in Figs. 2 and 3.

The insulating block II, which may comprise an insulating member of any suitable material,

such as porcelain, is preferably substantially rectangular in plan and in elevation. It is provided with a pair of apertures l3, l4 extending from top to bottom and adapted to receive the rivets i5, IS.

.The rivet serves to support the fixed condenser plate which is fixedly secured to the insulating member l2. This fixed condenser plate may comprise a sheet metal member having the substantially rectangular plate body l8, which is disposed above the insulating support l2. Plate body l8 has an aperture IQ for passing the rivet l5 which clamps it tothe insulating mempoint 22, extending across the edge of the insulating block i2, and it is formed with a depending connector formation comprising a tongue of metal 23, having a suitable aperture 24.

The shape and arrangement of such a connector is shown in greater detail with respect to the connector 25, having aperture 25,. which forms a part of the upper removable condenser plate, and is shown in elevation in Fig. 4.

This connector tongue may have partially circular grooves 21 located opposite each other at the point of juncture between the connector tongue 25 or 23 and the body of the condenser plates so as to weaken the connector tongues along a line between the grooves 21. This causes the connector tongues to bend along this line, rather than in the body of the connectors, where the stock is also quite narrow, due to the formation of the apertures 23 and 26.

In order to permit the two condenser plates to be brought very closely together, without electrical conducting contact, the rivet |5 also secures above the plate IT a thin sheet of mica 28, which also has an aperture 29 for passing screw bolt 2|, and an aperture for receiving the rivet I5, which clamps the mica 28 and plate H to the insulating support |2.

The mica sheet 28 preferably extends far enough to cover the upper end of rivet IE to eliminate any possibility of contact between the upper plate and the rivet, and the mica sheet may be substantially rectangular in section, completely covering the fixed condenser plate H,

The screw bolt 2| may comprise a threaded and headed metal member, the head 30 being adapted to engage the top of the movable condenser plate 3| to draw it into closer proximity to the fixed plate [1.

The threaded shank 32 of the screw bolt 2| may be threaded into the body of the insulating member l2; that is, the bore 33 in the insulating member may be formed with threads, and this is the preferred mode of construction when the insulating member is made of Bakelite or a fiber strip. Where a porcelain insulating member I2 is employed, as in Fig. 3, this porcelain block is preferably formed with a non-circular socket 34 communicating with the lower end of bore 33 and adapted to receive the non-circular nut 35, such as an ordinary hexagonal nut. This nut is held against turning by the walls of the socket 34, and it forms the fixed threaded con-,

nection between the screw bolt 2| and the insulating block |2. In such case, the bore 33 is of sufllclent size to permit sliding movement of the threaded shank 32 in the bore, as the screw bolt progresses in the nut 35.

The movable condenser plate 3| comprises a sheet metal member, which is formed with a substantially rectangular body portion 36, having an enlarged centrally located aperture 31 for slidably passing the shank 32 of screw bolt 2| The movable condenser plate 3| differs from the simple rectangular form in having the partially circular cut-outs or grooves 38, 39 at each end of the plate adjacent to and concentric with the heads of rivets l5 and IS. The rivets l5 and I6,

having heads which project above the insulating plate l2, would otherwise come into contact with the movable plate first, and the proximity of these two irregular metal bodies or rivets to the movable flat plate 3| might otherwise completely change the characteristics of the adjustment of the condenser.

At the rear of the movable condenser plate 3| it is provided with a pair of resilient pintle extensions 40, 4|, comprising integral strips of metal located one on each side of the cut-out 39, the cutout in this case actually being an aperture with the circular end 42 straight opposite end 43, and straight sides 44, 45.

These resilient pintle extensions are preferably bent upward in partially cylindrical form so as to resiliently support the plate 3| and to urge the plate 3| upward into engagement with the head 3|) of screw bolt 2|.

The pintle extensions 40, 4| have their ends integrally joined to an attaching flange portion 46 which extends downward at right angles to the plane of the face of the insulating block |2. The attaching portion 46 carries the integral connector formation 25 having the aperture 26, and has the opposite slots 21 to weaken the connector at the point of juncture and facilitate bending, as described.

Both the condenser plates I1 and 3| and the parts integral therewith are constructed of relatively thin resilient sheet. metal which has a tendency toward flexibility, and the movable condenser plate 3| is preferably supported on the insulating block |2 by a bracket 41 of thicker and stifier material.

The bracket 41 may comprise a sheet metal member of relatively stiff stock, having an attaching flange 48, which may be of substantially triangular form, as shown in Fig. 5. Attaching flange 48 has an aperture 49 for passing the rivet 16, which also passes through the bore 14 in the insulating member l2 and clamps the attaching flange 48 of bracket 41 fixedly to the insulating block |2.

The attaching flange 48 supports the upwardly extending body portion 5|! of the bracket 41, which body portion is at right angles to the attaching flange 48, and which lies against the flat rear edge of the block |2. The flat engagement between the rear edge 5| of the block and the forward face of the body portion 50 of the bracket 41 serves to prevent rotation on the rivet l5, and

the single rivet l6 secures this bracket to the insulating member and prevents all movement thereof.

The bracket 41 is provided with a pair of clamping fingers 52, 53, which preferably are located in slots 54, 55, respectively, in the attaching flange portion 45 of the movable condenser plate 3|.

These clamping fingers 52, 53 preferably fit quite closely in the slots 54, 55, thereby preventing any vertical movement, in Fig. 4, of the attaching flange portion 46 with respect to the clamping fingers 52, 53. The clamping fingers 52, 53 extend around the edge of the portion 46, and are bent into substantially U shape against the rear side of the flange portion 45. Since the fingers 52, 53 extend in opposite directions toward each other, they effectively and permanently secure the portion 46 of the condenser plate 3| to the bracket 41.

The attaching flange 48 of the bracket 41 is preferably arranged under the insulating member |2 so as to prevent interference between this flange 48 and the upper condenser plate 3|, to which it would be adjacent if it were on the upper side.

Another reason for placing the attaching flange of trimmer condensers constructed according to the present invention do not vary due to the action of the pull of any lead on a connector.

In some embodiments of the invention the bracket 41 may also be employed for securing the fixed condenser plate I! to the opposite edge of the insulating block l2, but the embodiment illustrated is preferred, as the single rivet attachment for the fixed plate [1 appears to be adequate.

While I have illustrated a preferred embodiment of my invention, many modifications may be 1 made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth. but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. In'a trimmer condenser, the combination of an insulating supporting plate with a fixed condenser plate comprising a sheet metal member having a flat body and a flat connector flange extending at right angles thereto, said insulating plate being of substantially rectangular shape in plan and elevation. and means. for securing said flat body to one side of said insulating platewith said connector flange flatly engaging the edge of said plate, a movable condenser plate comprising a sheet metal member having a body portion similar in shape to the shape of the fixed condenser plate and connected to a supporting flange portion by a pair of spaced and resilient pintle members. said securing flange portion extending at right angles to the body portion of said movable condenser plate and having a connector formation at its end and a bracket having a securing flange engaging the bottom of said insulating plate and secured thereto by securing means and having an,upwardly extending flange engaging the edge of said insulating plate, and means for securing said upwardly extending flange to the securing flange of said movable condenser plate.

2. In a trimmer condenser, the combination of an insulating supporting plate with a fixed condenser plate comprising a sheet metal member having a flat body and a flat connector flange extending at right angles thereto, said insulating plate being of substantially rectangular shape in plan and elevation, means for securing said flat body to one side of said insulating plate with said connector flange flatly engaging the edge of said plate, a movable condenser plate comprising a sheet metal member having a body portion similar in shape to the shape of the fixed condenser plate and connected to a supporting flange portion by a pair of spaced and resilient pintle members, said securing flange portion extending at right angles to the body portion of said movable condenser plate and having a connector formation at its end and a bracket having a securing flange engaging the bottom of said insulating plate and secured thereto by securing means and having an upwardly extending flange engaging the edge of said insulating plate, and means for securing said upwardly extending flange to the securing flange of said movable condenser plate, comprising a pair of fingers carried by said upwardly extending flange extending about the securing flange of said movable condenser plate and clamping said securing flange to said vertically extending flange.

3. In a trimmer condenser, the combination of an insulating supporting plate with a fixed condenser plate comprising a sheet metal member having a flat body and a flat connector flange extending at right angles thereto, said insulating plate being of substantially rectangular shape in plan and elevation, means for securing said flat body to one side of said insulating plate with said connector flange flatly engaging the edge of said plate; a movable condenser plate comprising a sheet metal member having a body portion similar in shape to the shape of the fixed condenser plate and connected to a supporting flange portion by a pair of spaced and resilient pintle members, said securing flange portion extending at right angles to the body portion of said movable condenser plate and having a connector formation at its end and a bracket having a securing flange engaging the bottom of said insulating plate and secured thereto by securingmeans and having an upwardly extending flange engaging the edge-of said insulating plate, and means for securing said upwardly extending-flange to the securing flange of said movable condenser plate, comprising a pair of fingers carried by said upwardly extending flange extending about the securing flange of said movable condenser plate and clamping said securing flange to said vertically extending flange, said securing flange of said movable condenser plate having slots for reception of said fingers to determine the position of said securing flange within said fingers. v

4. In a trimmer condenser, the combination of an insulating supporting plate with a fixed condenser plate comprising a sheet metal member having a flat body and a flat connector flange extending at right angles thereto, said insulating plate being of substantially rectangular shape in plan and elevation, means for securing said flat bodyto one side of said insulating plate with said connector flange flatly engaging the edge of said plate, a movable condenser plate comprising a sheet metal member having a body portion similar in shape to the shape of the fixed condenser plate and connected to a supporting flange portion by a pair of spaced and resilient pintle members, said securing flange portion extending at right angles to the body portion of said movable condenser plate and having a connector formation at its end and a bracket having a securing flange engaging the bottom of said insulating plate and secured thereto by securing means and having an upwardly extending flange engaging the edge of said insulating plate, means for securing said upwardly extending flange to the securing flange of said movable condenser plate, comprising a pair of fingers carried by said upwardly extending flange extending about the securing flange of said movable condenser plate and clamping said securing flange to said vertically extending flange, said securing flange of said movable condenser plate having slots for reception of said fingers-to determine the position of said securing flange within said fingers, and threaded means supported by said insulating plate and engaging said movable condenser plate to regulate the spacing of the condenser plates.

LAWRENCE C. JOHNSON. 

